The size of the fee depends on the flight, with longer flights charging more. American provided the following introductory fees: $19 for St. Louis to Chicago, $29 for San Francisco to Dallas/Fort Worth or from Boston to Chicago, and $39 for New York City to Los Angeles or from Honolulu to Chicago.

This is the just latest so-called "ancillary" fee for the hard-hit airline industry, which has been charging passengers in the last couple years for a number of services that were once included in the fare. This includes checked luggage, meals, non-alcoholic drinks, pillows, extra leg room and so on.

"[Passengers] were not able to choose these seats previously," said American Airlines spokeswoman Stacey Frantz. "Now they can choose these specific seats, if they want them, for a small fee."

Frantz said that disabled passengers will continue to get priority seating for the front coach section, and they will not be charged extra for it.

While the ancillary fees have annoyed some passengers, it has proven to be a boon for the industry. The Air Transport Association of America reported last month that passenger revenue was on the rise for the first half of the year, including a 25% surge in June compared to the same period the year before. The fees were partly responsible for the increase.

When that report was released in July, ATA spokesman David Castelveter said the rise in revenue stemmed from "a combination of improving economic conditions, increase in business travel and revenue from ancillary fees."